Installation for signalling a motor vehicle deceleration comprising a light emitting a steady light flow

ABSTRACT

The invention relates to an installation for signalling the deceleration of a motor vehicle. It comprises a signal lamp having an illuminating area divided into luminous sections, each equipped with its own light source, and means for controlling the lighting of a number of light sources which increases with the deceleration of the vehicle. The luminous intensity of the illuminating area remains substantially constant whatever the number of lighting sections lit. This constant intensity can be obtained by supplying the light sources with substantially constant power. The means for controlling the lighting of the light sources comprise a deceleration sensor and connection means which selectively link the light sources to an electrical-energy source as a function of an output signal from the sensor.

BACKGROUND OF THE INVENTION

The invention relates to an installation for signalling the decelerationof a motor vehicle, comprising a signal lamp having an illuminating areawhich lights up in the event of deceleration of the vehicle, thisilluminating area being divided into lighting sections, each sectionbeing equipped with its own light source, and means for controlling thelighting of a number of light sources which increases with thedeceleration of the vehicle so as to obtain a lit surface of theilluminating area representative of this deceleration.

The stop lamps placed at the rear of a vehicle light up when the brakepedal is actuated. They thus allow the driver of a following vehicle toanticipate a slowing-down and to react to it. In contrast, these lampsgive no information on the strength of the braking. For this reason stoplamps have been envisaged (DE 195 06 621), particularly complementarylamps, the illuminating area of which is divided into a certain numberof sections. The greater the deceleration of the vehicle, the higher thenumber of sections lit up. The surface of the illuminating areaincreases in size as a function of the deceleration and thus supplies anindication representative thereof. This allows the driver of a followingvehicle to be informed as to the strength of the braking.

However, in a known lamp of this type, each section of the illuminatingarea emits a luminous flux of constant intensity. The overall intensityof the lamp is thus equal to the arithmetic sum of the intensities ofeach of the sections, such that it varies very greatly. It is a minimumwhen only one section is lit and a maximum when all the sections are.However, the luminous intensity of the lamp should not exceed a maximumvalue fixed by the regulations. If this value is not exceeded when allthe sections are lit, the lamp will be difficult to discern when onlyone single section is lit since its luminous intensity will be weak. Ifthe luminous intensity of a single section is sufficient to be discernedclearly, the amplitude of the variation of the signal, proportional tothe total number of sections of the lamp, will have to be low so thatthe intensity of the lamp does not exceed the maximum value when all thesections are lit. Hence the known lamps do not make it possible fully totransmit a signal representative of the deceleration, which has theoutcome either of late braking by the following vehicle, or ofover-braking followed by acceleration.

BRIEF SUMMARY OF THE INVENTION

The precise subject of the invention is an installation for signallingthe deceleration of a motor vehicle which remedies these drawbacks. Itshould make it possible to deliver a signal representative of thedeceleration which can vary by a large amplitude while being perceptibleat low deceleration, and do so without the intensity of the lampexceeding the regulatory standards when the lamp is fully lit.

This result is achieved, in accordance with the invention, by the factthat the luminous intensity of the illuminating area remainssubstantially constant whatever the number of lighting sections lit.

The constant luminous intensity of the illuminating area is preferablyobtained by supplying the light sources with substantially constantpower.

By virtue of this characteristic, the lamp delivers a signal which canvary by a large amplitude while being perceptible even for a slightdeceleration, this being so without the intensity of the lamp exceedingthe regulatory standards when the lamp is fully lit.

According to one particular embodiment, the light sources are such thatthe voltage at their terminals is largely independent of the strength ofthe current which is passing through them, the substantially constantluminous intensity of the illuminating area being obtained by supplyingthe light sources with an electric current of substantially constantstrength. These light sources consist, for example, of a plurality oflight-emitting diodes.

The means for controlling the lighting of a number of light sourceswhich increases with the deceleration of the vehicle preferably comprisea deceleration sensor which measures the deceleration of the vehicle,and connection means which selectively link the light sources to anelectrical-energy source as a function of an output signal from thedeceleration sensor.

The connection means preferably comprise, for each light source, atransistor mounted on the circuit for supplying power to the source anda comparator, receiving an output signal from the deceleration sensorand linked to the transistor, which changes over when the output signalfrom the deceleration sensor becomes higher than a reference voltage,which makes the transistor conduct.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention willemerge further on reading the description which follows of embodimentexamples described by way of illustration, by reference to the attachedfigures. In these figures:

FIG. 1 is a diagrammatic view of an installation in accordance with theinvention;

FIG. 2 is a view of a preferred embodiment of the invention;

FIG. 3 represents a signal lamp in which the lighting sections arearranged concentrically.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, the signal lamp 2 comprises a housing 4 which encloses acertain number of light sources 6. Each light source may consist of asingle lamp, for example a neon tube, or of a series of lamps, forexample a series of light-emitting diodes. The light sources 6 areseparated by partitions 8 which divide the internal space of the housing4 into as many sections as there are light sources. The overallilluminating area of the lamp 2, formed by a bezel 10 which closes thehousing, is therefore divided into a number of sections equal to that ofthe light sources.

The light sources 6 are linked to a source of electric current via meanswhich make it possible for the luminous intensity of the illuminatingarea to remain constant whatever the number of lighting sections lit. Inthe example represented, these means consist of a power regulator 20which delivers a constant power. The regulator is linked to connectionmeans 22 which selectively link the light sources to theelectrical-energy source as a function of the output signal delivered bythe deceleration sensor 24. When the deceleration is slight, theconnection means close only the switch 26 so that only the first sectionof the illuminating area is lit up. If the deceleration increases, thenit is switch 28 which is closed, which lights up the second section, andso on up to switch 30. At that time, the whole of the lamp 2 is lit up.The lit surface of the illuminating area is therefore a function of thedeceleration. It may be proportional to this deceleration, for example.The lamp thus supplies information representative of the deceleration,which allows a following vehicle to react to it under the bestconditions. Moreover, however, the luminous power of the lamp remainssubstantially equal whatever the number of illuminating sections lit byvirtue of the presence of the power regulator. When only one lightsource is powered, it absorbs all the power supplied by the regulator20. When two light sources are powered, the power is distributed overthese two sources. And when all the light sources are powered, the poweris distributed over all the light sources. Hence the luminous power ofthe lamp remains substantially constant. By virtue of thischaracteristic, the surface of the illuminating area may vary by a largeamplitude between the two extremes, namely a slight slowing (a singlesection lit) and emergency braking (lamp entirely lit), and do sowithout exceeding the limits fixed by the regulatory standards.

The electronic diagram of a preferred embodiment of the invention hasbeen represented in FIG. 2. In this embodiment, each light sourceconsists of a series of light-emitting diodes. As is known, the voltageat the terminals of the light-emitting diodes is substantially constant(to within 20%), as a function of the strength of the current whichpasses through them. It is therefore possible to carry out fairlysatisfactory power regulation by regulating only the strength of thecurrent absorbed by the diodes. A current regulator 32 is formed by thetwo transistors 34 and 36.

A lamp 2 which includes only three sections has been represented in thefigure, but this number could naturally be much higher. One of thelighting sections, called first section 36, is linked directly to thesource of electric current, without passing through the connection means22. It lights up as soon as the switch 44, actuated by the brake pedal(not represented), is closed, independently of the value of thedeceleration. The other sections 38 and 40 light up as a function of theoutput signal from the deceleration sensor 24. In a variant embodiment,the information accessible on a network carrying information inmultiplexed form can be used in place of the deceleration sensor.

The connection means 22 comprise a transistor 46 and a comparator 48 forthe second illuminating section 38, and a transistor 50 and a comparator52 for the third illuminating section 40. The second illuminatingsection 38 lights up when the output signal from the deceleration sensor24 is above a reference voltage given by the resistor 54. The transistor46 becomes conducting, which connects the light source 6 of the secondsection 38 to the source of electric current and lights up this lightsource.

If the deceleration increases further, the output signal from thedeceleration sensor 24 increases and goes above a higher referencevoltage given by the resistors 54 and 56. The transistor 52 [sic}becomes conducting which connects the light source 6 of the thirdsection 40 to the source of electric current and lights up this section.The lamp is thus completely lit.

The installation further includes, conventionally, a protection 58against overvoltages. The resistors in the power-supply Lines of each ofthe sections serve to balance the current in the light-emitting diodes.

Another possible configuration of the illuminating sections has beenrepresented in FIG. 3. The lamp 2 is circular, and it is divided intoconcentric sections. The lamp can be designed in such a way that thecentral section 36 lights up first, then the sections 38 and 40. Or,conversely, the section 40 may light up first, then the section 38 andfinally the central section 36, the luminous intensity of the lampremaining substantially constant in all cases.

What is claimed is:
 1. An installation for signalling the decelerationof a motor vehicle, comprising a signal lamp having an illuminating areawhich lights up in the event of deceleration of the vehicle, thisilluminating area being divided into lighting sections, each sectionbeing equipped with its own light source, and means for controlling thelight of a number of light source, and means for controlling thelighting of a number of light sources which increases with thedeceleration of the vehicle so as to obtain a lit surface of theilluminating area representative of this deceleration, wherein theluminous intensity of the illuminating area remains substantiallyconstant whatever the number of lighting sections lit.
 2. Aninstallation according to claim 1, wherein the constant luminousintensity of the illuminating area is obtained by supplying the lightsources with substantially constant power.
 3. An installation accordingto claim 1, wherein the light sources are such that the voltage at theirterminals is largely independent of the strength of the current which ispassing through them, the constant luminous intensity of theilluminating area being obtained by supplying the light sources with anelectric current of constant strength.
 4. An installation according toclaim 3, wherein the light sources consist of a plurality oflight-emitting diodes.
 5. An installation according to claim 1, whereinthe means for controlling the lighting of a number of light sourceswhich increases with the deceleration of the vehicle preferably comprisea deceleration sensor which measures the deceleration of the vehicle,and connection means which selectively link the light sources to anelectrical-energy source as a function of an output signal from thedeceleration sensor.
 6. An installation according to claim 5, whereinthe connection means comprise, for at least one light source, atransistor mounted on the circuit for supplying power to the source anda comparator, receiving an output signal from the deceleration sensorand linked to the transistor, which changes over when the output signalfrom the deceleration sensor becomes higher than a reference voltage,which makes the transistor conduct.
 7. An installation according toclaim 2, wherein the light sources are such that the voltage at theirterminals is largely independent of the strength of the current which ispassing through them, the constant luminous intensity of theilluminating area being obtained by supplying the light sources with anelectric current of constant strength.
 8. An installation according toclaim 2, wherein the means for controlling the lighting of a number oflight sources which increases with the deceleration of the vehiclepreferably comprise a deceleration sensor which measures thedeceleration of the vehicle, and connection means which selectively linkthe light sources to an electrical-energy source as a function of anoutput signal from the deceleration sensor.
 9. An installation accordingto claim 3, wherein the means for controlling the lighting of a numberof light sources which increases with the deceleration of the vehiclepreferably comprise a deceleration sensor which measures thedeceleration of the vehicle, and connection means which selectively linkthe light sources to an electrical-energy source as a function of anoutput signal from the deceleration sensor.
 10. An installationaccording to claim 4, wherein the means for controlling the lighting ofa number of light sources which increases with the deceleration of thevehicle preferably comprise a deceleration sensor which measures thedeceleration of the vehicle, and connection means which selectively linkthe light sources to an electrical-energy source as a function of anoutput signal from the deceleration sensor.
 11. A method of signalingdeceleration of a motor vehicle, comprising: selectively controlling alighting of a number of light sources to selectively illuminate sectionsof an illuminating area according to an amount of deceleration of amotor vehicle; maintaining a luminous intensity of the illuminating areaat a substantially constant intensity irrespective of a number ofsections illuminated.
 12. The method according to claim 11, wherein theconstant luminous intensity of the illuminating area is obtained bysupplying the light sources with substantially constant power.
 13. Themethod according to claim 11, wherein a voltage at terminals of thelight sources is substantially independent of a strength of currentpassing therethrough, the constant luminous intensity of theilluminating area being obtained by supplying the light sources with anelectric current of constant strength.
 14. The method according to claim13, wherein the light sources comprises a plurality of light-emittingdiodes.
 15. The method according to claim 11, wherein the controllingcomprises: measuring the deceleration of the vehicle; and selectivelylinking the light sources to an electrical-energy source as a functionof the measured deceleration.
 16. The method according to claim 15,wherein the linking comprises connecting a light source of the lightsources to a power supply via a transistor, the transistor beingconductive to enable supply of power to the power source if the measureddeceleration exceeds a predetermined value.
 17. The method according toclaim 11, wherein the number of light sources illuminated increases withincreased deceleration of the motor vehicle.
 18. The method according toclaim 11, wherein the plurality of illuminating sections are arrangedconcentrically.